1. Field of Invention
The present invention relates to a diffuser tube for diffusing gases in a processing tank used in a sewage-treatment facility and the like.
2. Description of the Related Art
FIG. 8 shows an example of a conventional diffuser device for sludge, which is formed of a vinyl chloride (PVC) tube 1 provided with a plurality of diffusion holes 2 having a diameter of about a few millimeters. The conventional diffuser device has drawbacks that, when the diffusion operation stops, the sludge comes into the interior of the tube through the diffusion holes 2 and clogs them up.
In order to prevent the ingress of the sludge, rubber membrane-type diffuser devices have been put into practical use. However, due to a higher pressure-loss during the diffusing operation, the rubber membrane-type diffusers require a higher power for blowers, resulting in an undesirable increase in power consumption.
For example, Japanese Patent No. 3353225 describes such a conventional diffuser device which is an aerator. As shown in FIG. 9, the aerator has a flat base 3 and an expandable sheet 4 disposed on the flat base 3. A number of slits 5 are formed in the sheet 4 such that a pressurized gas is supplied through the slits 5 into a liquid such that numerous bubbles are formed in the liquid. By making the shape of the slits 5 formed in the sheet 4 in a non-straight line, the sheet 4 is prevented from tearing at the slit portions, whereby the tearing problems is overcome.